Download Does dietary knowledge influence the eating behaviour of

Editorial
Does dietary knowledge influence
the eating behaviour of adolescents?
more than 40% of their daily energy and fat intake from out of home
meals with the students having a low intake of fruit and vegetables
and a high intake of fat.11
In order to develop a true understanding of adolescents’ eating
behaviour and food choices it is necessary to briefly consider such
behaviour from an ecological perspective.1 Four levels of influence
impact on the nutritional health of teens. Firstly, individual or
intrapersonal factors such as the psycho-social and biological factors
immediately drive behaviour. Secondly, the social environment (or
interpersonal factors) in which the adolescent lives, in terms of
peers and family members, plays a strong role. Thirdly, one needs
to place the adolescent in the perspective of his/her community and
environment in terms of influences impacting on nutrition-related
behaviour. Outside influences such as availability and access to
fast food outlets, school tuckshops, food stores and vendors in the
vicinity may play a role in his/her decision making. Lastly the macroenvironment needs to be understood in terms of the society in which
the adolescent finds himself/herself. The latter influences include
effects of mass media and advertising1. For example, research in the
USA since the nineties has shown that advertisements on children’s
programmes on television are frequently the direct opposite of the
recommended diet. They are mainly for fast foods and for foods rich
in sugar and fat. Very few, if any promulgate a fruit and vegetable
intake.2
In South Africa there is little published data on adolescent food
patterns and nutrition-related knowledge. The article by Venter et
al in this issue of the SAJCN on dietary fat knowledge and intake of
mid-adolescents attending public schools in the Bellville/Durbanville
area of the city of Cape Town12 provides important information on
dietary fat intake and knowledge of fat in the diet, especially when
seen in the light of the food-based South African dietary guideline
“eat fat sparingly”. For nutrition professionals the information has
great merit. We learn that food items contributing most to total fat
intake of these middle to upper income adolescents are margarine/
butter, full cream milk and cheese or cheese spread. Full cream milk
and cheese are used by the learners 30% and 24%, respectively,
five or more days a week. Additionally, many other sources of fat are
consumed 3–4 times a week, including fried chicken, red meat, cold
cuts, salad dressing/mayonnaise, doughnuts, and potato crisps.12
Sadly, knowledge on dietary fat was evaluated as poor in 52% of
the group with only 25% knowing the lowest fat containing food and
26% the highest energy source of food.12 The good news for nutrition
and health professionals is the finding that those learners who had
the best nutrition scores were also those who reported being very
interested in nutrition. Furthermore, the majority of learners who
achieved average or good scores indicated nutrition incorporation
in a school subject as their source of nutrition information. The
association between fat knowledge and fat intake of learners was
significant with those having a higher knowledge score also having
a more desirable (prudent) fat intake.
Many studies have reported that adolescents frequently consume
an energy-dense diet which is of poor quality in terms of essential
micronutrients.3-6 This is attributed to many factors including low
meal frequency; skipping breakfast; high consumption of sweetened
beverages; increased consumption of energy-dense foods; increased
consumption of food away from home; and skipping meals.3-6 In the
USA, food choices of adolescents do not meet the Dietary Guidelines
for Americans; the diet is low in fruits and vegetables and dairy
products and high in fat.7 Furthermore, a British study8 has reported
data from national surveys in 1997 and eight years later. Sugarsweetened beverages remained the most popular choice of snack
after eight years; however the frequency of consumption and the
portion sizes were significantly higher.
This last finding is of crucial importance to developing and fostering
healthy dietary practices in adolescents. It appears that dietary
knowledge has an effect on nutrition behaviour and furthermore
that this knowledge can be imparted at school. The literature shows
that there have been many curriculum-based school nutrition
programmes which have improved knowledge and eating behaviour
of schoolchildren. The majority of these have been undertaken in
primary schools in children aged between 8 and 11 years. Some
of the best known examples are Pathways, CATCH, Kansas Lean,
CHIC, Know Your Body and Eat Well and Keep moving.13-18 In these
studies nutrition knowledge improved significantly after a nutrition
curriculum taught by teachers. Furthermore, dietary fat intake
decreased significantly in all these studies. Know Your Body was one
In developing countries, urban residence and high socioeconomic
status have been positively associated with frequency of intake of
energy-dense foods in adolescents.9-11 A study in Costa Rica noted
that 30% of adolescents exceeded the American Heart Association
dietary recommendations for total fat and saturated fat and 50%
reported a higher cholesterol intake.9 In China, a study by Shi et
al10 found that high socioeconomic status and urban residence were
positively associated with intake of high-energy foods such as foods
of animal origin. In Benin it was noted that adolescents consumed
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2010;23(2)
Editorial
of few studies which evaluated their intervention results after ten
years. They found that the favourable serum changes at baseline
were maintained at 10 years.17 These included total cholesterol, LDL
cholesterol, HDL cholesterol and HDL-cholesterol ratio.
References
In high school adolescents there have been fewer school-based
interventions however, but three studies which showed significant
changes in knowledge and behaviour were TEENS, PATH and
VYRONAS.19-21 TEENS, which was targeted at low income children
in grades 7 and 8 was aimed at improving fruit and vegetable
intake and decreasing fat intake of children using different types
of school-based interventions. The most significant decrease in
fat intake was in the intervention arm which included peer group
counselling in addition to a nutrition curriculum-based arm. PATH
was aimed at improving knowledge of minority students in grades 9
and 10. A nutrition education programme over 11 weeks resulted in
a significant improvement in dietary intake (decreased saturated fat
and cholesterol) and a significant improvement in dietary knowledge.
In VYRONAS, a 12 week school-based nutrition education-based
intervention resulted in a significant decreased energy and total fat
intake even after a year. It also needs to be noted that some schoolbased interventions did not result in significant behaviour changes
or showed very little improvement.22,23 Furthermore, long-term
evaluations of school-based interventions remain scarce.
3. Moreno LA, Rodriguez G, Fleta J, Bueno-Lozano M, Lazaro A, Bueno G. Trends of dietary habits in
adolescents. Crit Rev Food Sci Nutr 2010;50(2):106–112.
In terms of recommendations we should be reminded of the burden
of the chronic non-communicable diseases (NCDs) in South Africa
and the associated high mortality rate from some of these diseases.24
Teenagers are on the brink of adulthood and it is likely that the
dietary habits which have been fostered by the family and school
will continue into adulthood. A low fat and saturated fat intake, on
its own, is not adequate for the prevention of NCDs. Engelfriet et
al25 postulate that “broader adherence to recommendations for daily
intake of fruit and vegetables, fish and fatty acid composition may
take away as much as 20-30% of the burden of cardiovascular
disease and result in approximately one extra life year for a 40-yearold individual”.
13. Caballero B, Clay T, Davis SM, Ethelbah B, Rock BH, Lohman T et al. Pathways: a school-based,
randomized controlled trial for the prevention of obesity in American Indian schoolchildren. Am J Clin
Nutr 2003;78(5):1030–1038.
1. Story M, Neumark-Sztainer D, French S. Individual and environmental influences on adolescent eating
behaviors. J Am Diet Assoc 2002; 102(3Suppl): S40–51.
2. Temple N, Steyn NP.Food advertisements on children’s programs on TV in South Africa. Nutrition 24
(2008)781–782.
4. Li M, Dibley MJ, Sibbritt DW, Yan H. Dietary habits and overweight/obesity in adolescents in Xi’an City,
China. Asia Pac J Clin Nutr 2010;19(1):76–82.
5. Burgess-Champoux TL, Larson N, Neumark-Sztainer D, Hannan PJ, Story M. Are family meal patterns
associated with overall diet quality during the transition from early to middle adolescence? J Nutr Educ
Behav 2009;41(2):79–86.
6. Briefel RR. Wilson A, Gleason PM. Consumption of low nutrient, energy-dense foods and beverages at
school, home, and other locations among school lunch participants and nonparticipants. 2009; 109 (2
Suppl): S79–90.
7. Sebastian RS, Wilkinson Enns C, Goldman JD. US adolescents and MyPyramid: associations
between fast food consumption and lower likelihood of meeting recommendations. J Am Diet Assoc
2009;109(2):226–35.
8. Kerr MA, Rennie KL, McCaffrey TA, Wallace JM, Hannon-Fletcher MP, Livingstone MB. Snacking patterns
among adolescents: a comparison of type, frequency and portion size between Britain in 1997 and
Northern I relend in 2005. Br J Nutr; 101(1):122—31.
9. Mong-Rojas R. Dietary intake as a cardiovascular risk factor in Costa Rican adolescents. J Adolescent
Health 2001;28(4):328–37.
10. Shi Z, Lien N, Kumar BN, Holmboe-Ottesen G. Socio-demographic differences in food habits and
preferences of school adolescents in Jiangsu Province, China. Eur J Clin Nutr 2005;59(12):1439–48.
11. Nago ES, Lachat CK, Hybregts L, Roberfroid D, Dossa RA, Kolsteren PW. Food, energy and macronutrient
contribution of out of home foods in school-going adolescents in Cotonou, Benin. Br J Nutr
2010;103(2):281–8.
12. Current study. Dietary fat knowledge and intake of mid-adolescents attending public schools in the
Bellville/Durbanville area of the City of Cape Town. 2010;
14. Luepker RV, Perry CL, Osganian V, Nader PR, Parcel GS, Stone EJ, Webber LS. The child and adolescent
trial for cardiovascular health (CATCH). J Nutr Biochem 1998;9:525–534.
15. Harris KJ, Paine-Andrews A, Richter KP, Lewis RK, Johnston JA, James V. Reducing elementary school
children’s risks for chronic diseases through school lunch modifications, nutrition education, and
physical activity interventions. J Nutr Educ 1997;29:196–202.
16. Harrell JS, McMurray RG, Bangdiwala SI, Frauman AC, Gansky SA, Bradley CB.. Effects of a schoolbased intervention to reduce cardiovascular disease risk factors in elementary-school children: the
Cardiovascular Health in Children (CHIC) study. J Pediatr 1996;128(6):797–805.
17. Manios Y, Moschandreas J, Hatzis C, Kafatos A. Health and nutrition education in primary schools of
Crete: changes in chronic disease risk factors following a 6-year intervention programme. Br J Nutr
2002;88(3):315–324.
18. Gortmaker SL, Cheung LW, Peterson KE, Chomitz G, Cradle JH, Dart H et al. Impact of a school-based
interdisciplinary intervention on diet and physical activity among urban primary school children: eat well
and keep moving. Arch Pediatr Adolesc Med 1999;153(9):975–983.
Ideally, South African children should learn about good nutrition at
home and at school. There is sufficient convincing evidence that
school-based curriculum-based nutrition programmes significantly
increase children’s nutrition knowledge and improve their dietary
behaviour. Additionally, schools should develop school wellness
policies6 and limit access to unhealthier (high sugar, high fat) food
options on the premises. The HealthKick, a collaborative research
study of the MRC, HSRC and UCT Sports Science Institute is one
such intervention aimed at producing a nutrition and physical activity
curriculum for schools in South Africa to implement as part of Life
Orientation for grades 4–6. If successful in improving nutrition
knowledge and behaviour of children, it can serve as a model for
other schools.
19. Birnbaum AS, Lytle LA, Story M, Perry CL, Murray DM. Are differences in exposure to a multicomponent
school-based intervention associated with varying dietary outcomes in adolescents? Health Educ Behav
2002;29(4):427–443.
20. Fardy PS, White RE, Haltiwanger-Schmitz K, Magel JR, McDermott KJ, Clark LT, Hurster MM. Coronary
disease risk factor reduction and behavior modification in minority adolescents: the PATH program. J
Adolesc Health 1996;18(4):247–253.
21. Mihas C, Mariolis A, Manios Y, Naska A, Arapaki A, Mariolis-Sapsakos T, Tountas Y. Evaluation of a
nutrition intervention in adolescents of an urban area in Greece-and long-term effects of the VYRONAS
study. Public Health Nutr 2009;13(5):712–9.
22. Kain J, Uauy R, Albala C, Vio F, Ceda R, Leyton B. School-based obesity prevention in children;
methodology and evaluation of a controlled study. Int Journal Obesity 2004;28(4):483–493.
23. Bere E, Veierod MB, Bjelland M, Klepp KI. Outcome and process evaluation of a Norwegian schoolrandomized fruit and vegetable intervention: Fruits and Vegetables Make the Marks (FVMM). Health Educ
Res 2006;21(2):258–267.
24.Steyn K, Fourie J, Temple N (eds.). Chronic Diseases of Lifestyle in South Africa: 1995–2005. Parow:
MRC, 2005.
25. Engelfriet P, Hoekstra J, Hoogenveen R, Buchner F, Van Rossum C, Verschuren M. Food and vessels:
the importance of a healthy diet to prevent cardiovascular disease. Eur J Cardiovasc Prev Rehabil
2010;17(1):50–5.
Dr Nelia Steyn
Chief Research Specialist
Centre for the Study of the Social and Environmental Determinants
of Nutrition
Knowledge Systems
Human Sciences Research Council
Correspondence to: Dr Nelia Steyn, e-mail: [email protected]
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